Clutches are known to be used in an automatic transmission assembled to a power train of a vehicle. An increased number of clutches assembled into a transmission are also known to improve mileage performance of a vehicle. For example, a transmission having only four clutches does not perform as well, or provide as good mileage performance, as a transmission having six, or even eight clutches. Due to the increasing cost of fuel, most vehicle companies are engineering new transmissions having eight and even nine clutches.
A typical clutch includes an annular housing having an annular wall defining a plurality of spaced splines. Occasionally, the splines are formed in the annular wall by machining a substantially thicker housing when additional structural integrity is required. Inside the clutch housing, a piston is retained adjacent a base of the housing and circumscribes a transmission shaft through which oil flows in between the housing base and the piston. The piston is separated from the plurality of clutch plates by a steel spacer.
The splines that are defined by the annular wall of the housing extend to the distal end of the housing. A snap ring groove is formed into the splines by either a machining or a reverse lance-and-form process. A snap ring is inserted into the groove to retain the clutch components set forth above. Clutches typically fail because the weakness of the reverse lance-and-formed groove formed into the splines of the clutch housing. Sharp edges defined by the reverse lance create weaknesses in the housing that are known to crack, particularly when the transmissions are under heavy load. Attempts have been made to improve the integrity of the snap ring groove and the clutch housing by increasing the thickness of the clutch housing and extending the distance between the snap ring groove and the open end of the housing. None of these attempts to improve the integrity of the housing have proven sufficient. Furthermore, increasing the thickness of the housing adds weight to the vehicle transmission, particularly given eight clutches are becoming more prevalent in some transmissions. Furthermore, extending the distance between the snap ring groove and the end of the clutch housing makes use of packaging space unnecessarily causing increase inside a transmission. Therefore, there is a strong need to redesign the clutch and the clutch housing to reduce mass, increase structural integrity, particularly to retain the snap ring, and reduce the amount of packaging space required for a given clutch.